


Riveted

by Mercy_Run



Category: Undertale (Video Game)
Genre: Dark, Ecto-Genitalia (Undertale), Extremely Dubious Consent, Fixation, Fontcest, Incest, Language, M/M, Manipulation, Mental Instability, Monster Heat, Obsession, Smut, Somnophilia, Undertale Universe, Unhealthy Relationships, Voyeurism, Yandere Papyrus, Yet Darker Themes, darker, forced soul bond
Language: English
Status: Completed
Published: 2016-09-14
Updated: 2016-09-14
Packaged: 2018-08-14 23:44:45
Rating: Explicit
Warnings: Rape/Non-Con, Underage
Chapters: 1
Words: 3,563
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8033647
Author URL: https://archiveofourown.org/users/Mercy_Run/pseuds/Mercy_Run
Summary: Beautiful ivory bone, hazed eye-lights and flushed blue magic beneath him.  Sans was gorgeous, his beautiful and fragile older sibling."p-papyrus?"It was time to claim what was rightfully his.





	Riveted

**Author's Note:**

> READ THE TAGS! I CAN'T STRESS THIS ENOUGH!
> 
> Otherwise, I hope you enjoy this piece of trash that won the 500 Follower Celebration Poll I held on Tumblr.
> 
> mercy-run.tumblr.com ~<3

Papyrus hummed cheerfully to himself as he did the dishes, pelvis swaying in time with the mindless tune. The feel of warm water was comforting and familiar against his bare phalanges, suds slipping between the gaps. His teeth pulled into a delighted smile as he placed a clean plate aside before turning affectionate sockets on his older brother.

Sans was slumped back in a chair at the table, sockets shut and chin lowered to his collar bone. One of the sleeves of his jacket had fallen from a small shoulder, revealing the tantalizing sight of his diminutive bone structure. Papyrus’ smile stretched wider at the peaceful expression on the small skeleton’s face, breathing pattern deep and slow.

He picked up the mostly untouched plate of spaghetti deftly and stored it in the refrigerator for later. His sibling adored his cooking! It would be a waste to let it spoil!

Oh… That was right…

His smile curled into something devious as the taller skeleton realized there was no need for such bravado in his thoughts. Papyrus knew perfectly that his attempts at cooking were abysmal.

Sans didn’t need to know he knew! The monster was actually fond of the sight of his brother forcing mouthful after mouthful down until the plate was spotless. The gorgeous smile that the small skeleton offered him afterwards, without fail; was breathtaking. It was genuine and caused the skeleton’s soul to shiver in delight.

For Sans to soldier through the awful taste to lie through his teeth just to make him happy… 

It was so adorable and reaffirmed the fact that his older brother loved him every time Papyrus witnessed it.

That it occurred multiple times a day was just an added delight!

Once the chore was done, Papyrus whirled around, soul pounding in excitement as he approached the sleeping form of his brother. It was common for Sans to fall asleep at odd intervals. The poor thing didn’t sleep at all at night and when he did, nightmares chased the smaller skeleton into reality, Papyrus watching intensely between the tiniest of cracks in his sibling’s door.

The towering skeleton bent down and expelled an unnecessary breath against Sans’ face, running light finger-tips over the other’s cheek.

The limp skeleton didn’t stir, not that Papyrus expected him to. He smirked and leaned down to pick up the fork that had clattered to the floor during their shared dinner. Dropping his overly saccharine attitude, he flung it carelessly into the sink for later.

It didn’t matter that Sans’ sleep wasn’t natural, Papyrus had been careful to put the other’s portion of spaghetti in a separate container.

The secret ingredient he had slipped into his brother’s portion would make sure this night would be uninterrupted.

“Oh, how I have waited for this night, Sans…” He whispered against the other’s exposed shoulder, kissing the bone there with the utmost reverence.  
The sweet and cloying scent of his brother’s heat cycle beginning this morning had made him burst out into delighted laughter, drawing a happy but slightly confused expression from the smaller skeleton.

It had been three years since his darling older brother last experienced a cycle. For some reason, Sans had been unable to reach that level of happiness and sense of safety heat cycles required. The small skeleton had spent a lot of time in the basement that he didn’t think Papyrus was aware of. The nightmares had gotten worse and he had thought this night would never present itself.

Three years prior, it wouldn’t have been proper for Papyrus to bond with his older brother. He had still been considered a babybones and the taller skeleton wouldn’t inconvenience Sans by causing a scandal.

He carefully slid Sans out of the chair, slipping his arms under the small shoulders and knees to cradle the other skeleton to his chest, his humming picking up again as he carried Sans to his room.

It had been such a long wait, but his patience had been rewarded.

Papyrus laid the smaller skeleton on the mattress and merely stood over his brother, sockets drinking in the delicious sight spread across his bed.

Sans’ cheeks were flushed cyan, teeth parted slightly as if not getting enough air through his nose aperture. His small hands were laying palm up, his normal guard lowered; completely open.

“You are so exquisite, big brother…” Papyrus breathed out; worshipful, “it has been a long three years…”

He stripped, mind already filled with everything he wanted to do to Sans.

The mattress squeaked as the larger skeleton settled on the foot of the bed but Papyrus ignored it. The drug he had used was strong and even if Sans woke up; heat rendered a monster’s thought process difficult underneath the carnal desire of heat.

Breathing deeply of his older brother’s agitated magic, Papyrus reflected on the first time he had the honor to view Sans’ heat cycle. He had been eight at the time, still a naive babybones when he had crept to his sibling’s room upon hearing a disturbance at an ungodly hour.

What he had seen had changed his young mind forever.

Sans had been young at the time too, barely fourteen but already working three jobs to support them. Curious, Papyrus had remained shrouded by the darkness; peeking through the crack. Even smaller back then, but still smelling and appearing like the vision his brother made now; Sans had been laying rib-cage down on the bed.

Of course; he had been confused but his magic had responded to the way his older brother’s hips canted desperately against his own hand. The lovely whimpers and moans couldn’t be completely contained by the other hand plastered over his teeth. Seeing his normally cool and collected sibling falling apart had been a turning point.

After that night, Papyrus had observed Sans with a keen and unwavering interest.

Sans had still been child, just like himself; yet he worked like an adult. Much harder than many, in fact. There were shadows burnt under the other skeleton’s sockets; a permanently exhausted air about him.

Why, brother? He had questioned, almost hearing his much younger voice even now.

Sans had been confused by the sudden question and asked what he meant.

Why do you work so hard?

His older brother had smiled then, just as he did for Papyrus everyday. Sans’ normal grin was a farce. But this sincere and gorgeous smile was all for him.

Because I love you, Papyrus. He had answered.

The words had been uttered so firmly, so resolutely; that his young mind blanked before he urgently demanded how much Sans loved him.

More than the stars, lil’ bro. More than everything.

He had been forever changed after that, ever watchful and fixated completely on Sans. His mind had reasoned that they were brothers. But didn’t brothers love each other only a little? That his growing fascination was merely because he had seen something normally reserved for adults? Sans’ glowing tongue oozing blue magic as he fucked himself with his hand-

But it wasn’t just that.

His infatuation burned into a consuming obsession the more Papyrus’ thoughts had lingered. There were some broken memories in his mind that the skeleton couldn’t understand, but Sans had been the one constant in his life. Fiercely protective, gentle and tender, his older brother never told him ‘no’ when he asked something of Sans.

When Sans had told him of his absolute status in the other’s soul, Papyrus knew that Sans was special. 

It was like he and Sans were the only true monsters that mattered in the Underground. Others had patronized his sweet sibling when asking for work sometimes, turning a blind eye to their struggle.

Surely all other monsters weren’t anything to raise a fuss about. The wretched creatures had ignored Sans’ desperate struggle to keep them both well-fed, protected and safe.

His older brother was precious and special. Priceless.

It was as if fate had designed Sans especially for him, even before Papyrus was brought into this world.

Sans belonged to him.

…and tonight, Papyrus would make certain that his older brother knew that, body and soul.

“I’m going to make you feel so good, brother,” he purred lowly, finally shifting his focus on ridding the smaller body of clothing. His expression softened in compassion as the skeleton underneath him huffed out a tortured breath.

“I know, Sans,” he whispered, smiling when a soft, needy whine slipped from between the other’s parted fangs when Papyrus’ hands brushed faintly against bone as he slid the other’s track shorts down, tossing them aside.

He was no stranger to touching Sans whilst he was sleeping. Papyrus had to be utterly certain that his sibling wouldn’t reject his advances, so he had been conditioning the other to yield to his magic. To be familiar with the resonance Papyrus emitted when his mask for the world was lowered.

The younger skeleton had lost track of how many times he had stolen into Sans’ room, checking to see if he was awake before pleasuring the smaller skeleton whilst unaware.

Papyrus had never, ever penetrated his sweet sibling. No, that would’ve been a transgression, a betrayal. Spurting gooey orange magic against Sans’ tongue had been acceptable.

But this…. Oh this would be heavenly…

He savored the sight of Sans once more, his lingering gaze taking in the blue magic flushing the other’s face and small knees. The other monster was panting now that cool air brushed the mound of magic formed in response to Papyrus’ intent. Fingering the wet folds, the younger skeleton felt the heavy weight of his own tongue forming. Blue slick was already oozing against his fingers.

Sans was so ready and he had already been so fucking patient...

“p-papyrus?”

His gaze snapped up to his older brother’s face, finding the other’s eye sockets barely open. There was a puzzled expression in the other’s hazy blown eye-lights.

Sans was awake.

Instead of the panic he expected, Papyrus felt heightened arousal lance through his soul. It seems that his brother may have built up a tolerance for the drug.

The other’s mouth formed a few aborted words between ragged gasps for air, Sans’ mind seemingly frozen from embarrassment or just unable to puzzle out the current situation.

Papyrus smiled slowly and thumbed the other’s clit, reveling in the harsh and breathy moan his sibling made. He loomed like a predator over his much smaller brother, licking his teeth at the delectable squirming.

“wha-i-paps-?” The other’s voice quivered under the force of his stare, Papyrus' right socket smoking orange light as his tongue dragged slowly over his teeth.

“Hello brother~” Papyrus murmured, sliding two fingers into Sans’ dripping slit and driving them home with a satisfying 'squelch’.

Sans cried out sharply, pelvis already moving against Papyrus’ fingers even though his mind was scattered.

“i-we-oh stars!”

The younger brother hummed, pleased as he finger-fucked the heated monster below him, the evidence of Sans’ excitement sliding down his wrist.

“You’re so beautiful, Sans,” Papyrus cooed, his own magic collecting at his pelvis before forming into a formidably sized shaft. The flash of fear that crossed his brother’s expression was wiped away as long fingers struck the back of his pussy.

“ah!”

“Falling apart like this was only a matter of time,” the younger sibling murmured lowly, almost threatening in tone, “you have been driving me crazy with your scent all day.”

Sans whimpered, a line of drool slipping down his chin as a range of expressions warred for priority on his flushed face.

“The other creatures looking at you with lust… It filled me with urgency.” He confessed and was pleased when the smaller skeleton’s eyes hazed over, visibly giving up on understanding how this had happened. If this was merely a dream…

“Those filthy creatures probably envisioned themselves defiling you. You are mine, brother.” He paused, this was one last chance for Sans to deny him and he had to work slyly. Quickly. His fingers stilled inside his sibling’s clenching magic.

If Sans rejected him now…

Well, there was a reason Papyrus never visited the Hall in the King’s Castle.  
Blown eye-lights trained on his face as Papyrus’ expression screwed into insecurity and sadness.

“You love me, right? You have told me so many times, brother…” His voice was laced with genuine fear.

Sans’ sockets squinted and then trailed to the right, as if trying to remember something. Likely why this shouldn’t occur. Why he should say 'no’. His brother was alarmingly good at talking him into an impasse.

“I want you, Sans.” Papyrus pleaded, though his body was tight; ready to wrap a hand around that small and fragile neck.

To squeeze…

“papyrus…” His name was uttered unsurely.

To watch that one singular hope **snap.**

Oh Sans… He was so fragile.

“Give yourself to me, brother,” he whispered, “it’s all I ever wanted.”

The smaller skeleton’s inner war was exposed for him to witness. Confusion dominated all. Uncertainty causing Sans’ eye-lights to flick to the side, as if chasing an errant thought.

His fingers curled up inside of his small brother, snapping those lights back to his face.

“…you love me… Right, brother?” Papyrus asked, voice shaking from fear and rising killing intent.

Don’t LAsh Out yet! One HP!

A thrill of exhilaration chased away the violence when Sans’ reason crumbled under the pressure of choosing logic over his love for Papyrus, small arms reaching out; accepting him.

He immediately buried his face into the very neck he had been toying with snapping, smirking victoriously.

The Great Papyrus always wins!

Phalanges once again picking up, the taller skeleton basked in happiness as Sans writhed underneath him.

It was finally happening.

His dream come true.

“Oh brother,” Papyrus murmured against the other’s sweaty skull, nipping on the vertebrae, “you can’t imagine how happy I am. I have been waiting so long!”

Sans’ magic gushed around his hand as his delicate sibling found release for the first time that night, wailing and clinging to Papyrus in a way that caused him to bite down.

“fuck, paps! oh stars, hnn!”

His oozing appendage licked the tears from his brother’s sockets hungrily.

Finally. Finally!

“I have you. I’ll always have you.” He gingerly nudged his larger femur between Sans’ thighs that had reflexively closed during his release, “open up for me, brother.”

Papyrus was finally going to do what he had fantasied hundreds of times before, magic throbbing impossibly hard against his slumbering brother all of those nights.

The tip of his orange ecto-cock slipped against Sans’ dripping slit before he reached down with a bare hand and steadied himself-

Oh…

Sans was swallowing him up, pressed breath-takingly tight around his long shaft, his cunt nearly too small to physically take him. The tiny skeleton’s sockets had widened, blown pupils growing larger as his brother arched into the intrusion, forcing him ever deeper-

Fuck, Sans felt heavenly!

This was better than he had ever imagined!

“please…please, papyrus…please!” Sans was chanting deliriously as the larger skeleton finally sank fully into his sibling.

They were one.

He was inside Sans.

“Oh brother, you feel sublime!” Papyrus groaned worshipfully, pulling back and thrusting back in. Sans’ tongue lolled from between his fangs, whining.

“please!” He begged desperately and the younger brother wasted no more time before setting a brutal pace, pushing Sans’ magic flushed knees up and apart.

Yes! Yes!!

His scent was mingling with his brother’s. Sans cries of his name rivaling the smile Papyrus adored.

…But it still wasn’t enough!

Growling low and feral, Papyrus violently claimed his older sibling’s mouth, his ecto-tongue wrapping multiple times around Sans. Small arms wrapped around his shoulders as orange mixed with cyan.

Papyrus’ hand was already up his brother’s rib-cage; fingers closing around the small pulsing white organ before Sans noticed.

It was his soul, of course Sans would notice.

The small body jerked underneath him and Papyrus opened his sockets as he drew the soul out of his sibling, holding the glowing organ as he leaned back.  
Information filtered through his mind, so so much. Nearly enough to topple his already tattered sanity.

Even through the haze of his heat, Sans’ sockets grew wide and dark.

Terrified.

Papyrus’ hips slowed to a smooth and slow pace, a snarl rumbling angrily in his rib-cage. There were all of those secrets he had been chasing, exposed for him to see.

Resets. A human. Pain. Death and dust.

He had been killed over and over.

Red and gold, the air singing with powerful energy and despair. His scarf wrapped around that neck he now regretted even thinking of snapping.

That ABHORRENT human had KILLED his brother! Sans! What was his!?

Sans was trembling now, unable to move because the culmination of his being was being held captive by Papyrus.

His gaze gentled and he leaned back, still joined with his smaller brother as he removed his own soul. There was a flash of terror and understanding that flickered across Sans’ face when his soul was bared.

“n-!”

They touched and Sans’ expression slackened as their magic began to mix, his denial dying into a moan.

“You aren’t the only one who had secrets, Sans,” he murmured as Papyrus pressed their souls even closer together.

There was a token resistance.

A single second in time that Sans was allowed to realize that Papyrus was a murderer, with enough LOVE to rival that human. That he had been lying to him. To everyone.

Their souls merged completely and that instant was gone forever.

Horror eased into acceptance. Acceptance into admiration. Admiration into an echo of Papyrus’ obsession.

Sans’ smile was as beautiful and genuine as ever, but his tone was breathy.

“paps…”

Worshiping...

Their merged souls created a dripping sienna color.

He watched, fascinated as Sans’ eye lights changed; phasing into cyan from it’s normal white. There were orange rings around them.

They were complete. Bonded together.

Papyrus recognized that tilt in Sans’ grin and returned the unhinged smile with one of his own. He didn’t have to pretend anymore. Sans knew. _He knew all of Sans._ No more secrets. No more doubting himself.

Sans was his now. Completely and utterly.

As their souls separated and he released them, the force of Sans’ heat returned tenfold and caused the smaller skeleton to scream, thrashing against Papyrus’ still buried cock in desperation for relief from the inferno. His hips snapped punishingly, nearly painfully as he began a frantic pace.

“papyrus! fuck me harder! faster~” Sans’ voice was pitched a tone higher in his delirium. The taller skeleton growled and pinned the smaller skeleton’s wrists down, the bed rocking, creaking in protest underneath the delightful noises of his brother begging.

Willingly. Awake.  
All his.

“If anyone touches you like this, sees you like this; I will murder them; Sans!” He snapped and his brother’s sockets widened before wild joy sung through their connected souls.

“yeeessss…” Sans hissed out, moaning at a particularly vicious thrust.  
“You’re mine!” Papyrus growled and his older brother shuddered, changed eye lights rolling as he came hard around Papyrus’ cock, clamping down.

“yes!” Sans screamed in response and that was what had his pace stuttering and he was tipping over the edge-

Papyrus shook as he came violently, nearly whiting out from the pleasure. His breathing was similar to Sans ragged gasps for air as he felt their mixed magic soaking the sheets, ruining them. His burning eye lowered to Sans’ face, finding an expression there that usually meant Sans was sleeping peacefully.

But he was awake, cyan and orange pupils opening to train adoringly on his younger brother. The endless well of depression he had experienced for that brief second when Sans had last been an individual was gone forever.

Papyrus had tipped the smaller skeleton into a madness identical to his own.  
And they were joined forever now.

His longer phalanges brushed against Sans’ and they linked fingers as Sans continued to smolder, his heat far from being satisfied. But his soul’s desire was finally reality. His older brother was linked to him, their merged magic screaming to the Underground shamelessly that they were bonded.

Papyrus smirked.

Their souls were one. His LOVE bleeding over into Sans. He remembered the human. Knew about the 'resets’. Nothing could break or undo a soul bond.  
Even time itself…

“I will murder that repulsive human for you, brother~” Papyrus cooed, grin widening at the elation flashing in the other’s eye-lights, “over and over and over…”

Realization snapped from Sans’ end of the bond.

“i’m not alone anymore.” he breathed, as if all of the world’s worries had been lifted from his delicate shoulders.

Insecurity and worry flashed through their bond, over even the arousal Sans was radiating.

“the others…”

“Don’t matter. Only you matter Sans. It was always only you; in my eyes." 

"paps…”

“I love you.”

It didn’t matter how crazy Papyrus was. His corruption of his older brother didn’t matter.

It was a physical ache to finally be able to confess with full knowledge that he would be accepted. After all, Sans had no choice. He didn’t even desire to have a choice now.

And Sans. His sweet, tortured, amazing and freshly insane older brother smiled that same smile he had years ago.

“i love you too, papyrus. more than the stars. more than everything.”


End file.
